The invention relates in general to electronic communications systems, and in particular to a Wireless Optical System for Multidirectional High Bandwidth Communications.
There are many applications where computers and other devices require connection to a central network. Currently these network connections are established using either wired or radio frequency systems which each have their own limitations and costs. For example, there is a high dollar cost associated with running category 5 wiring to establish network connections due to the cost of the wiring, the labor involved to run the wiring, and the labor involved with termination of the wires as well as the removal of the wiring previously used to network the systems together. On the other hand, the utilization of Radio Frequency (xe2x80x9cRFxe2x80x9d) communication may avoid some of the costs associated with copper wiring, but at the expense of physical security of the link since the information placed on the network via RF is typically easy to intercept and decode.
However, data signals for networks can be imposed upon optical signals, such as light, laser light and light from light emitting diodes (LEDs) by various types of modulation. On the other hand, it is common knowledge that optical signals have other problems. For instance, light reflects from surfaces it encounters creating multipath signal interference to one degree or another. Even with indoor, short range, applications, movement of an optical transmitter with respect to the optical receiver (due to very small changes in their position, for example as a byproduct of building movement or vibration of the surface(s) on which the node(s) are mounted) can produce unwanted multi-path interference on a time varying basis. The result is that the optical channel, though it is pure line-of-sight, is an extremely hostile channel. Thus, optical systems (i.e. laser- and/or LED based) typically are only used for short distances and in point-to-point (not omni-directional or multidirectional) systems where the cumulative atmospheric and multipath uncertainty is small. These systems typically can only establish reliable communication channels at levels well below the theoretical data transfer limits for optical systems.
What is needed, therefore, is a device to provide cost efficient deployment, fast installation, and secure optical communications to groups of users needing access to a central network.
The previously mentioned needs are fulfilled with various embodiments of the present invention. Accordingly there is provided, in a first form, an optical communications system comprising a multi-directional optical transmitter/receiver adapted to receive transmit optical signals from multiple directions and a multitude of uni-directional optical transmitter/receivers adapted to communicate with the multi-directional optical transmitter/receiver, where the multi-directional optical transmitter/receiver dynamically adjusts a beam to locate and align with the unidirectional optical transmitters/receivers. Additionally, the uni-directional optical transmitter/receivers adjust their beams to locate and align with the multi-directional optical transmitter/receiver. Also provided is a method for optical communication between an optical access point and a user optical terminal comprising: searching for a signal from the user optical station, handshaking with the user optical station, registering the user optical station, determining the location of the user optical station, assigning the time slot for the user optical station, allocate a minimum capacity to the user optical station, allocate a priority to the user optical station, and establishing a network communication link between the optical access point and the user optical station.
Different embodiments of the invention overcome the limitations of security, the costs associated with the physical wiring, the labor to reroute wiring, and the limitations of where wiring can be quickly deployed when wired networking is used, to connect multiple users on a network.
A unique feature of one aspect of the present invention is the combination of multidirectional communication, digital processing, and network management which together minimizes the effects of the hostile optical channel. This is done by combining communication lasers and/or LEDs with optics that will direct the signal so as to limit the opportunity for reflections, and signal processing techniques to further limit the effect of multipath, and to reduce the effects of atmospheric degradation of the wireless transmission channel. This combination results in the ability to reliably provide performance at levels much closer to the maximum theoretical limits for a given distance between transmitter and receiver.
Another aspect of one embodiment of this system is the use of a reflective primary optical element for a panoramic coverage optical system. This permits the use of multi-spectral optical processing with wavelengths that differ greatly, but without the aberrations that refractive primary optics would generate. For infrared wavelengths in particular, this is of great benefit, since useful wavelengths often differ by a factor of two or more, making reflective optics very desirable. In a similar way, reflective optics provide benefits for other forms of optical diversity such as polarization. It is common knowledge that stress in refractive optics can create non-uniform transmittance of light with various polarizations. If polarization diversity is used as a degree of freedom or channel orthogonality, then such non-uniformity is undesirable. The benefits described here are not exhaustive, and reflective primary optics provide similar benefits to other forms of diversity not described here.
Another unique aspect of this system, particularly when implemented with a rotating reflecting body, is the opportunity to use different optical paths and power (or gain) for the transmit and receive functions through utilization of different portions of the reflective surface for the respective signals. This allows for reduction in self-interference, for simultaneous transmit and receive operation in a plurality of directions, and for the option of different solid angle coverage for the transmit and receive functions.
These and other features, and advantages, will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings. It is important to note the drawings are not intended to represent the only form of the invention.